Nanosized NiO-Ti0.94V0.06O1.94B0.06 p-n junction (70-90 nm) with enhanced photocatalytic activity under visible light was prepared by a two-step sol-gel method. In order to simulate the density of state and band structure, the supercells (2 x 2 x 1) of pure TiO2 and doped TiO2 were calculated by first-principles with the plane-wave ultrasoft pseudopotentials method. The obtained samples were characterized by differential thermal analysis, X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and photoluminescence emission. It was revealed that the sample was highly crystalline anatase and formed a p-n junction with NiO phase. B atoms incorporated into the TiO2 lattice in the form of interstitial B and substitutional B. V atoms substituted Ti sites in the form of V3+ and V4+. The photocatalytic activity was evaluated by the degradation of Rhodamine B under visible light. Compared with TiO2, TiO1.94B0.06, Ti0.94V0.06O2, and Ti0.94V0.06O1.94B0.06, the NiO-Ti0.94V0.06O1.94B0.06 exhibited much higher photocatalytic activity (12.38 x 10(-3) min(-1)), which can be ascribed to the synergistic effects of the V/B co-doping by narrowing the band gap (2.36 eV) and the p-n junction heterostructures by reducing the possibility of recombination of photogenerated electron-hole pairs.